1. Field of the Invention
The present invention relates to a power source apparatus having a power factor correction circuit function, and particularly to operation in a critical mode of a bridgeless power factor correction circuit of a power source apparatus.
2. Description of the Related Art
Conventionally, in order to supply electric power to a load, a power source apparatus in which an AC (alternating current) voltage from an input AC power source is rectified and then converted to a desired AC or DC (direct current) voltage and supplied to the load has been widely used. In this kind of power source apparatus, a power factor correction circuit needs to be provided in order to correct the power factor and reduce the EMT noise generated by the power source apparatus. Therefore, in a general constitution of a power source apparatus, a rectification circuit consisting of a diode bridge and a power factor correction circuit consisting of a boost converter circuit are installed in the input stage.
In recent years, in a power source apparatus, a so-called bridgeless power factor correction circuit, in which a front stage diode bridge is made unnecessary by combining a power factor correction function by a boost operation and a rectification function, has been proposed (for example, refer to Japanese Patent Application Laid-Open (JP-A) No. 2011-152017). In this power factor correction circuit, the input stage of the power source apparatus can be constituted by a simple circuit and the conduction loss of the diode can be reduced, and thus this kind of power factor correction circuit is advantageous over a constitution in which the rectification circuit and the power factor correction circuit are provided separately.